The one hour special sees The Doctor in war-torn England embarking on a magical and mysterious adventure with a young widow and her two children. It will be directed by newcomer to Doctor Who, Farren Blackburn. From the BBC:

The special, set during World War II, sees Madge Arwell and her two children, Lily and Cyril, evacuated to a draughty old house in Dorset, where the caretaker is a mysterious young man in bow tie, and a big blue parcel is waiting for them under the tree. They are about to enter a magical new world and learn that a Time Lord never forgets his debts...